1. Field of the Invention
The present invention relates to a self-aligning roller bearing.
2. Description of Related Art
A known self-aligning roller bearing is described, for example, in Japanese Patent Application Publication No. 2012-17770 (JP 2012-17770 A). As shown in the vertical sectional view of FIG. 9, the self-aligning roller bearing includes an outer ring 81, an inner ring 84, spherical rollers 86, an annular cage 88, and an annular guide ring 90. The outer ring 81 has an outer raceway surface 82 in its inner periphery. The inner ring 84 has two rows of inner raceway surfaces 83 in its outer periphery. The spherical rollers 86 are arranged in two rows between the outer raceway surface 82 and the two rows of inner raceway surfaces 83. The cage 88 holds the spherical rollers 86 arranged in each row. The guide ring 90 is arranged between the cage 88 and the inner ring 84, and between the two rows of spherical rollers 86.
The cage 88 has a ring 91 and a plurality of cage bars 92. The ring 91 is positioned between the two rows of spherical rollers 86. The cage bars 92 extend from both sides of the ring 91 in an axial direction. In each row of spherical rollers 86, a space is formed between adjacent cage bars 92 in a circumferential direction of the cage 88 and serves as a pocket 94 which contains (holds) a corresponding spherical roller 86. The pocket 94 has its pocket surfaces facing the spherical roller 86; the pocket surfaces are constituted of side surfaces 92a of the adjacent cage bars 92 in the circumferential direction and a side surface 91a of the ring 91 in the axial direction.
The ring 91 of the cage 88 is provided with a contact portion 93 in the inner periphery of the ring 91. The contact portion 93 can contact an outer circumferential surface 90a of the guide ring 90. With this structure, the cage 88 is positioned in a radial direction by the guide ring 90. Further, a clearance is provided between the contact portion 93 and the guide ring 90 in the radial direction, and another clearance is provided between the inner ring 84 and the guide ring 90 in the radial direction. Accordingly, the guide ring 90 can independently and freely rotate with respect to the inner ring 84 and the cage 88.
As described in the above, the spherical rollers 86 are each contained in the pocket 94 of the cage 88. Further, predetermined clearances are provided between each spherical roller 86 and the pocket 94 (the pocket surfaces) so that the spherical roller 86 can rotate on its roller center line.
In such a self-aligning roller bearing, the spherical roller 86 may be rotated, by a small angle, on an imaginary line L1 passing through a contact point P1 at which the spherical roller 86 contacts the outer raceway surface 82 and a contact point P2 at which the spherical roller 86 contacts the inner raceway surface 83. In this case, an end surface 86a of the spherical roller 86 may contact a side surface 90b of the guide ring 90. In particular, when the spherical roller 86 on a first side (i.e. left side in FIG. 9) in the axial direction and the spherical roller 86 on a second side (i.e. right side in FIG. 9) in the axial direction are rotated in different directions (as indicated by arrows r1 and r2 in FIG. 9), the guide ring 90 is caught by the spherical rollers 86 on both sides of the guide ring 90 in the axial direction, which may cause abrasion of the guide ring 90 or the like. Further, abrasion powder from the guide ring 90 may be scattered onto the raceway surfaces, adversely affecting the life of the bearing.